1. Field of the Invention
The present invention relates to a superhard composite member consisting of a sintered body of cemented carbide or the like with diamond grains, dispersed therein to form a composite and a method of manufacturing the same.
2. Description of the Background Art
It is well known that a sintered body of WC cemented carbide or the like containing diamond is manufactured using an ultra high-pressure vessel at a pressure of 5.5 GPa and a temperature of 1500.degree. C. under thermodynamically stable conditions (refer to Japanese Patent Laying-Open No. 53-136790 (1978), Japanese Patent Publication No. 61-58432 (1986), U.S. Pat. No. 5,158,148 and the like). However, disadvantageously, the sintered body manufactured by such a technique is expensive and restricted in shape.
Japanese Patent Laying-Open No. 7-34157 (1995) (prior art 1) discloses a technique of sintering the material under thermodynamically instable pressure and temperature conditions for diamond in a solid phase thereby preparing a diamond composite member without employing an ultra high-pressure vessel, as one of the proposals for solving the aforementioned problem.
Japanese Patent Laying-Open No. 6-287076 (1994) (prior art 2) discloses a technique of direct resistance heating and pressurized sintering an inclination functional member having an inclination mixed layer consisting of a metal and ceramics between members of the metal and the ceramics with a molding outer frame and upper and lower push rods. In this case, the molding outer frame serving as one of electrical paths is varied in thickness thereby forming a temperature gradient which is responsive to an inclined composition. The term "inclination mixed layer" indicates a layer having an inclined composition, i.e., a concentration gradient (composition change) of the components.
On the other hand, U.S. Pat. No. 5,096,465 (prior art 3) discloses a technique of preparing a composite member containing metal-coated superhard grains of diamond or CBN in a binder phase by infiltration.
In the prior art 1, however, the material is sintered in a solid phase, and hence bonding strength between the diamond and a metal binder is so insufficient that the diamond may drop out of the binder.
The prior art 2 is not directed to a diamond composite member, dissimilarly to the present invention.
In the infiltration of the prior art 3, the diamond variance depends on the grain sizes of the added diamond, i.e., the packing density of the diamond grains, and hence it is difficult to prepare a composite member having an arbitrary diamond variance with arbitrary diamond grain sizes. Further, it is difficult to prepare a dense composite member by the infiltration, and this disadvantage is particularly remarkable in a large-sized or heteromorphic member.
Thus, there has been a long felt need for a strong diamond composite member having a sufficiently dense and homogeneous structure, which is prepared without employing an ultra high-pressure vessel.